Tsu escaped to Hong Kong in 1950 after the Kuomintang left mainland China. He was later ordained a Priest in Rome on 14 March 1959. Tsu was the editor of Kung Kao Po, a Catholic newspaper in Hong Kong, from 1959 to 1965. On 1 July 1967, he was appointed Auxiliary Bishop of Hong Kong and Titular Bishop of Orrea. After the resignation of Lorenzo Bianchi, he was appointed bishop of Hong Kong.